The present invention relates to a disc drive microactuator, and more particularly to a high resolution head positioning mechanism having a compliant joint serving as a center of rotation to enable rigid body motion of the system.
The density of concentric data tracks on magnetic discs continues to increase (that is, the size of data tracks and radial spacing between data tracks are decreasing), requiring more precise radial positioning of the head. Conventionally, head positioning is accomplished by operating an actuator arm with a large-scale actuation motor, such as a voice coil motor, to radially position a head on a flexure at the end of the actuator arm. The large-scale motor lacks sufficient resolution to effectively accommodate high track-density discs. Thus, a high resolution head positioning mechanism, or microactuator, is necessary to accommodate the more densely spaced tracks.
One promising design for high resolution head positioning involves employing a high resolution microactuator in addition to the conventional lower resolution actuator motor, thereby effecting head positioning through dual-stage actuation. Various microactuator designs have been considered to accomplish high resolution head positioning. However, many of these designs require deformation of the disc drive flexure or load beam to achieve small displacement of the head.
While these microactuators do preserve many of the manufacturing processes currently in existence by utilizing standard components, additional bending modes are generated in the load beam that have a negative effect on the performance of the microactuator and the associated servo control system that controls the movement of the microactuator. In order to accommodate the additional bending modes of the load beam, it is necessary to redesign the servo system to have substantially greater bandwidth, which requires significant additional design time and expense. In addition, the forces required to bend the stainless steel components of the disc drive, such as the load beam, are relatively high in relation to the size constraints of the microactuator. Therefore, there are significant design challenges to overcome in order to implement a microactuator that provides the requisite force to bend the load beam, which adds time and expense to the design process, and limits the range of technologies that maybe employed to realize the microactuator.
There is a need in the art for an effective disc drive microactuator design that utilizes rigid body motion of disc drive structures such as the gimbal and load beam in order to microposition the transducing head over a selected track of the rotating disc.
The present invention is an assembly and method for finely positioning a slider carrying a transducing head with respect to a selected track of a rotatable disc in a disc drive system. The disc drive system includes a movable actuator arm to effect coarse positioning of the slider. A suspension load beam has a proximal end connected to an actuator arm and a distal end for applying pre-load force to the slider. A flexure has a first end and second end, the second end supporting the slider. A compliant joint attaches the first end of the flexure to the suspension load beam between the proximal end and the distal end. A high resolution microactuator is operatively coupled to the flexure and the suspension load beam to deform the compliant joint and thereby effect rigid body movement of the flexure with respect to the suspension load beam upon operation of the motor. Alternatively, the compliant joint may be provided to attach the proximal end of the suspension load beam to the actuator arm, and the microactuator motor may by operatively coupled to the actuator arm and the suspension load beam to deform the compliant joint and thereby effect rigid body motion of the suspension load beam with respect to the actuator arm upon operation of the motor.